Current efforts for third generation partnership project (3GPP) long term evolution (LTE) systems are to update the technology, architecture and methods in the new LTE settings and configurations. These efforts would improve spectral efficiency, reduce latency, and improve radio resource utilization in order to provide faster user data rates and richer applications and services with less cost.
As part of these efforts, the 3GPP is proposing to introduce the concept of a home evolved Node-B (HeNB) in LTE systems, and in a parallel fashion, HeNBs may be introduced in Release 8 wideband code division multiple access (WCDMA), global system for mobile communications (GSM) enhanced data rates for GSM evolution (EDGE) radio access networks (GERANs) and other cellular standards. The HeNB refers to a physical device that may be similar to a wireless local area network (WLAN) access point (AP), which may be designed in a manner that allows access to cellular services to users over extremely small service areas, (e.g., homes or small offices). This can be particularly useful in areas where cellular networks have not been deployed and/or legacy RAT coverage exists, and in areas where cellular coverage may be faint or non-existent for radio related reasons, (e.g., an underground metro or shopping mall). The subscriber, (e.g., an individual or an organization), can deploy a HeNB over an area where such service is desired.
The HeNB is intended to connect to an operator's core network by using, for example, public internet connections available freely in homes and businesses across the country made available, for example, by direct subscriber line (DSL). This can be particularly useful in areas where LTE has not been deployed, and/or legacy 3GPP radio access technology (RAT) coverage already exists. This may also be useful in areas where LTE coverage may be faint or non-existent as a result of radio transmission problems that occur while being in an underground metro or a shopping mall, for example. The cell, which is the area of radio coverage provided by the HeNB, that is deployed by the HeNB may be accessed only by a group of subscribers who have access to the services of the cell, known as a family, and such a cell may be referred to as a HeNB cell or, more commonly, a closed subscriber group (CSG) cell. An HeNB may be used to deploy one or more CSG cells over the area that LTE coverage is desired. A CSG cell is a cell deployed by either an HeNB for LTE services, or by a home Node-B (HNB) for WCDMA or other legacy 3GPP RAT systems. A WTRU subscriber, (associated with an individual or an organization), may deploy a CSG cell, (listed on a white accessible to the WTRU subscriber), using an HeNB over an area where LTE service is desired. On the other hand, a macro-cell may be accessed by any WTRU that is not barred.
It has been proposed that a wireless transmit/receive unit (WTRU), as part of its white-list configuration, also be configured with the physical layer cell identifiers (PCIDs) of the CSG cells to which it has access. These PCIDs may correspond to any combination of the primary synchronization channel (P-SCH) and the secondary synchronization channel (S-SCH), or some other form of physical (PHY) layer identification for the CSG cells. It has also been proposed that a WTRU be able to request that a measurement/cell-search gap be allocated to it for CSG cell measurements/search, whereby this request may be triggered by a manual CSG cell search initiation. This measurement gap represents a point in time when the WTRU is tuned away from the serving cell such that it can search for suitable CSG cells in the vicinity.
Currently, it has been proposed that the WTRU read the master information block (MIB) and system information block (SIB) of the CSG cells in connected mode to decide if the upper-layer identity of the CSG cell, (e.g., the global cell identity of the CSG cell), is part of its white list. Furthermore, it has been proposed that the WTRU may tune away autonomously creating its own measurement gap, allowing it to read the SIB of the neighboring CSG cells.
However, several problems exist that need to be solved. For example, it has not been clearly established under what criteria the WTRU should use to autonomously tune away from the serving cell and read the CSG cell SIBs. Furthermore, it is not clear whether the WTRU generates continuous measurement gaps or disjoint measurement gaps, and if any indication needs to be sent by the WTRU when it autonomously tunes away from its serving evolved Node-B (eNB) or cell. Additionally, it is not clear whether the WTRU should report to the network that it has just detected a CSG cell or whether it has read and confirm the upper-layer identity.
While some tentative solutions have been proposed for active mode mobility between LTE macro-cells and CSG cells, no comprehensive solution incorporating different types of mobility has been developed as yet. Thus, a procedure that addresses the problems described above is desired, keeping in mind the restrictions imposed by the standardization bodies. It would therefore be beneficial to provide a method and apparatus for providing HeNB services to WTRUs.
A method and apparatus are proposed that provide a mechanism for a WTRU to measure and report CSG cells. Specifically, it proposes mechanisms that allow a WTRU to minimize the time taken to identify the CSG cell to which it has access.